The use of eDNA by as a robust, efficient, method to assess remote coastal islands for invasive terrestrial mammals

Abstract

Coastal islands, long known for their biodiversity amd unique ecology, face grave threats such as sea level rise, development, and biological invasions, among others. Despite this, basic knowledge of the prevalence of island dwelling species and their pressures is often lacking, and knowledge aquisition may be hindered by the logistics and costs of conducting offshore, or even nearshore, biological inventories. In light of the need for environmental practitioners to be able to survey islands quickly and efficiently, we test off-the-shelf commmerical environmental DNA water sampling equipment, universal primers, and commerical metabarcoding lab services, as tools to rapidy inventory coastal islands for mammalian biodiversity and invasive terrestrial threats. We collected enviromental DNA from sites (n = 35) on four coastal islands in Nova Scotia, from substrates including small turbid pools, dug wells, brackish coastal overwash, barachois ponds, and shallow emergent subsurface streams. Using a mammal-specific (MiMammal-U) metabarcoding markers, we detected the presence of invasive mammal species such as mouse (Mus musculus), rat (Rattus norvegicus), snowshoe hare (Lepus americanus), red squirrel (Tamiasciurus hudsonicus), could detected also conversely discharge after a haveay rainfall investigation is needed to upscale this promising approach as a powerful tool to monitor catch composition, assess the distribution of stocks, and generally record hanges in fish communities across the oceans coastal islands thaintroduced invasive species are present on all islandscan be used as an efficent tool to on the collected eDNA inventoried invasise nvase terestrail mammlas on all islands, species on all Our results sugegsrtion invebntory and monitoring an integra;l compenten necessary for efficet mangemten. Condition assseessemnt exotic species have expanded, and native species have gone extinct We investigate the use of environmental DNA obtained from water as a tool to assess the occurrence of non-native and problematic terrestrial mammals on remote coastal islands in Atlantic Canada.

Introduction

Use of environmental DNA to detect the present of terrestrial or semi-aquatic organisms is now well established (Ficetola, Miaud, Pompanon, & Taberlet, 2008; Harper et al., 2019; Leempoel, Hebert, & Hadly, 2020; Lyet et al., 2021; Neice & McRae, 2021; Saenz-Agudelo et al., 2022; Sales et al., 2020)

how robust the technology can be

Depending on the system and species, various studies have documented a positive correlation between the eDNA concentration measured and target species abundance or biomass

as a way We sampled environmental DNA, extracted from water, to assess terrestrial mammalian threats and biodiversity on coastal islands situated in a logistically challenging, ecologcially threatened, maritime landscape.s, We test the use of environmental DNA as a tool to provide such assessments, from the prespective of non-expert environmental practitioners in need of system that combines ease-of-use, robustness, and quality assurance. Our study sites fall within an archipelago in the province of Nova Scotia, Canada, which consists of some 4000 islands and skerries, many of which are threatened by rising sea levels, biological invasions, and human developement. As conservation organizations and governments move to prioritize and secure new island landholdings, there is increased need for rapid, cost-efficent assessment of island biodiversity and threats. To assess the diversity of native, problmatic native, and invasive terrestrial mammals on island To implement science-based conservation management and decision-making, a necessary first step is the detailed, on-the-ground assessment of species and their threats. Such lansdcapes have long relies on de facto conservation, due to remotmessn, and boost legal protection of exisiting island holdings, We investigate the use of environmental DNA obtained from water samples as a tool to assess diversity of terrestrial native, non-native, and problematic species,on remote coastal islands in Atlantic Canada.We investigate the use of environmental DNA obtained from water samples as a tool to assess diversity of terrestrial native, non-native, and probklematic species,on remote coastal islands in Atlantic Canada.

Alternative, direct methods include infrared cameras, hair tunnels, cage and snap trapping, some of which require intensive training, frequency checking, and extra levels of approvals and permitiing.

Coastal islands, globally, are threatened by changing climate, nonnative invasive or other problematic species, habitat degradation, among others. he lack of data and evidence that was underpinning environmental management

The purpose of this work is to continue the survey effort of breeding birds and their threats on coastal islands in Nova Scotia, and to catalyze effective action for conservation in a threatened region of high biological diversity and ecological uniqueness. The study site falls within one of Nova Scotia’s most diverse regions, and conservation actions in the area are an ongoing priority for the Canadian Wildlife Service, the Nova Scotia Department of Natural Resources and Renewables, and the Nova Scotia Nature Trust, among others. As conservation actions are largely based on fine-scale knowledge about species distributions and their threats, we aim to: A) conduct holistic inventories of birds and problematic mammal species in a key conservation area that has not been recently evaluated, and B) find ways to improve monitoring of wildlife and their threats by deploying new detection methods for invasive and problematic species through use of camera traps, acoustic sensors and eDNA. Our studies will help assess the ecological value of the region, and inform decision makers involved in the transfer of lands for inclusion within the protected areas network known as the Atlantic Canada Archipelago. Further, knowledge generated from our work will help identify and develop threat mitigation strategies and inform any future whole island restoration efforts.

Methods

Field sites and collection of samples

Figure 1. Water samples (n in parentheses) were collected on three Lobster Bay islands–Seal (26), Mud (2), and Flat (2)–and on Boot Island (4) in the Minas Basin, Nova Scotia. Samples on the Lobseter Bay

We collected water samples from 35 sites on four islands in Nova Scotia, Canada, between Setempter We deployed Moultrie A30i Series trail cameras at 19 sites. Ten units were set alongside attractants, which consistent of a bait made with oats, peanut butter, and molasses. Data from 12 units were collected during our stay on the island (nine of these units were retrieved from the field before departing the island), and ten other units were left for long-term data collection. Autonomous Recording Units (ARUs, aka BAR-LTs) were deployed at seven stations drawn from a spatially balanced master sample, which used the extent of Seal Islands as its bounds. The devices were programmed to initialize–i.e., to wake from sleep mode and commence recording–on 1 June 2022. At that time, devices will record continuously and maximize the chances of detecting diurnal or nocturnal birds occupying sites during the core breeding season (i.e., June–July); memory and battery power available to devices should produce ~28 days of continuous recordings. Finally, we collected 30 water samples for eDNA analysis (n_samples in parentheses), across Mud Island (2), Flat Island (2), and Seal Island (26). We filtered distilled water in the same manner as the other field samples, as a negative control. All samples were collected using a Smith-Root backpack sampler and self-preserving 1.2 micron filters. Samples were submitted to Precision Biomonitoring for analysis. Lab analysis will employ MiMammal universal primers, primers that have previously been shown to detect North American mammal species.

Lab Analyses

Metabarcoding was MiMammal primers (Ushio et al., 2017)

Results

Animals were detected on images collected from 11 of 12 devices. Often, dense nightly fog made the identification of species impossible, and potentially skewed our analyses(i.e., capturing less nocturnal activity). Detections include two days of records from two non-baited sites where water samples where also collected for eDNA; camera “11” (which corresponded to eDNA Sample ID 23) produced images of red squirrel (Tamiasciurus hudsonicus), snowsnow hare (Tamiasciurus hudsonicus), muskrat (Ondatra zibethicus), and Norway Rat (Rattus norvegicus; see notes on ID below); camera “12” (eDNA Sample ID 25) produced no images over two days.

Over three days, baited traps produced clear images of red squirrel, snowshoe hare, Norway rat, muskrat, Ring-necked Pheasant, and domestic sheep. While the presence of other small mammal species (e.g., Mus musculus, Mustela sp., Microtus pennsylvanicus, Peromyscus maniculatus, etc.) were not confirmed, two unclear images could not discount the possibility of the presence of some other small species. All images of rats were triggered at night, making species identification difficult. Images of rats with robust bodies and relatively short tails (with respect to the rest of the body length) are suggestive of Rattus norvegicus as opposed to Rattus rattus (aka “black” or “roof” rat). While the black rat is primarily found in the southern and Pacific coastal regions, of North America the species is known to move among ports via shipping routes.

Red squirrels were the first animal recorded in 4/11 cameras deployed, including one site that was unbaited. Snowshoe hare were recorded in all baited camera traps (10/10), and rats at 7 of 11 traps, which included an unbaited site were eDNA was also sampled, some 500 metres, as the crow flies, from the East Village. A camera deployed near the West Village produced a cluster of imagery consisting of three Ringed-neck Pheasant individuals (Figure 2).

Discussion

Conclusions

Acknowledgements

We thanks Jay Cashubec at Precision Biomonitoring for providing lab services, advice, and technical assistance.

Figures and Tables

Figure 1:

Figure 2:

Supplementary Materials

References

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